[Update][RFC][PATCH 6/8] PM / Sleep: Implement opportunistic sleep

From: Rafael J. Wysocki
Date: Tue Feb 07 2012 - 17:45:52 EST

On Tuesday, February 07, 2012, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@xxxxxxx>
>
> Introduce a mechanism by which the kernel can trigger global
> transitions to a sleep state chosen by user space if there are no
> active wakeup sources.
>
> It consists of a new sysfs attribute, /sys/power/autosleep, that
> can be written one of the strings returned by reads from
> /sys/power/state, a freezable ordered workqueue and a work item
> carrying out the "suspend" operations. If a string representing
> the system's sleep state is written to /sys/power/autosleep, the
> work item triggering transitions to that state is queued up and
> it requeues it self after every execution until user space writes
> "off" to /sys/power/autosleep. That work item enables the detection
> of wakeup events using the functions already defined in
> drivers/base/power/wakeup.c (with one small modification) and calls
> either pm_suspend(), or hibernate() to put the system into a sleep
> state. If a wakeup event is reported while the transition is in
> progress, it will abort the transition and the "system suspend" work
> item will be queued up again.

OK, so before somebody points that out to me, the completion was redundant
(it was a leftover from one of the previous versions of the patch, sorry
about that).

Moreover, try_to_suspend() is racy with respect to wakeup_count_store()
(in theory, an automatic suspend without checking wakeup sources may happen
if the latter is used carelessly when autosleep is enabled).

Thus below is an updated patch (it requires [8/8] to be updated too because
of the changes in pm_autosleep_set_state(), but that's rather trivial).

Thanks,
Rafael

---
From: Rafael J. Wysocki <rjw@xxxxxxx>
Subject: PM / Sleep: Implement opportunistic sleep

Introduce a mechanism by which the kernel can trigger global
transitions to a sleep state chosen by user space if there are no
active wakeup sources.

It consists of a new sysfs attribute, /sys/power/autosleep, that
can be written one of the strings returned by reads from
/sys/power/state, an ordered workqueue and a work item carrying out
the "suspend" operations. If a string representing the system's
sleep state is written to /sys/power/autosleep, the work item
triggering transitions to that state is queued up and it requeues
itself after every execution until user space writes "off" to
/sys/power/autosleep.

That work item enables the detection of wakeup events using the
functions already defined in drivers/base/power/wakeup.c (with one
small modification) and calls either pm_suspend(), or hibernate() to
put the system into a sleep state. If a wakeup event is reported
while the transition is in progress, it will abort the transition and
the "system suspend" work item will be queued up again.

---
drivers/base/power/wakeup.c | 38 ++++++++------
include/linux/suspend.h | 13 ++++-
kernel/power/Kconfig | 8 +++
kernel/power/Makefile | 1
kernel/power/autosleep.c | 112 ++++++++++++++++++++++++++++++++++++++++++++
kernel/power/main.c | 105 ++++++++++++++++++++++++++++++++++-------
kernel/power/power.h | 18 +++++++
7 files changed, 262 insertions(+), 33 deletions(-)

Index: linux/kernel/power/Makefile
===================================================================
--- linux.orig/kernel/power/Makefile
+++ linux/kernel/power/Makefile
@@ -8,5 +8,6 @@ obj-$(CONFIG_SUSPEND) += suspend.o
obj-$(CONFIG_PM_TEST_SUSPEND) += suspend_test.o
obj-$(CONFIG_HIBERNATION) += hibernate.o snapshot.o swap.o user.o \
block_io.o
+obj-$(CONFIG_PM_AUTOSLEEP) += autosleep.o

obj-$(CONFIG_MAGIC_SYSRQ) += poweroff.o
Index: linux/kernel/power/Kconfig
===================================================================
--- linux.orig/kernel/power/Kconfig
+++ linux/kernel/power/Kconfig
@@ -103,6 +103,14 @@ config PM_SLEEP_SMP
select HOTPLUG
select HOTPLUG_CPU

+config PM_AUTOSLEEP
+ bool "Opportunistic sleep"
+ depends on PM_SLEEP
+ default n
+ ---help---
+ Allow the kernel to trigger a system transition into a global sleep
+ state automatically whenever there are no active wakeup sources.
+
config PM_RUNTIME
bool "Run-time PM core functionality"
depends on !IA64_HP_SIM
Index: linux/kernel/power/power.h
===================================================================
--- linux.orig/kernel/power/power.h
+++ linux/kernel/power/power.h
@@ -269,3 +269,21 @@ static inline void suspend_thaw_processe
{
}
#endif
+
+#ifdef CONFIG_PM_AUTOSLEEP
+
+/* kernel/power/autosleep.c */
+extern int pm_autosleep_init(void);
+extern void pm_autosleep_lock(void);
+extern void pm_autosleep_unlock(void);
+extern suspend_state_t pm_autosleep_state(void);
+extern int pm_autosleep_set_state(suspend_state_t state);
+
+#else /* !CONFIG_PM_AUTOSLEEP */
+
+static inline int pm_autosleep_init(void) { return 0; }
+static inline void pm_autosleep_lock(void) {}
+static inline void pm_autosleep_unlock(void) {}
+static inline suspend_state_t pm_autosleep_state(void) { return PM_SUSPEND_ON; }
+
+#endif /* !CONFIG_PM_AUTOSLEEP */
Index: linux/include/linux/suspend.h
===================================================================
--- linux.orig/include/linux/suspend.h
+++ linux/include/linux/suspend.h
@@ -372,7 +372,7 @@ extern int unregister_pm_notifier(struct
extern bool events_check_enabled;

extern bool pm_wakeup_pending(void);
-extern bool pm_get_wakeup_count(unsigned int *count);
+extern bool pm_get_wakeup_count(unsigned int *count, bool block);
extern bool pm_save_wakeup_count(unsigned int count);

static inline void lock_system_sleep(void)
@@ -423,6 +423,17 @@ static inline void unlock_system_sleep(v

#endif /* !CONFIG_PM_SLEEP */

+#ifdef CONFIG_PM_AUTOSLEEP
+
+/* kernel/power/autosleep.c */
+void queue_up_suspend_work(void);
+
+#else /* !CONFIG_PM_AUTOSLEEP */
+
+static inline void queue_up_suspend_work(void) {}
+
+#endif /* !CONFIG_PM_AUTOSLEEP */
+
#ifdef CONFIG_ARCH_SAVE_PAGE_KEYS
/*
* The ARCH_SAVE_PAGE_KEYS functions can be used by an architecture
Index: linux/kernel/power/autosleep.c
===================================================================
--- /dev/null
+++ linux/kernel/power/autosleep.c
@@ -0,0 +1,112 @@
+/*
+ * kernel/power/autosleep.c
+ *
+ * Opportunistic sleep support.
+ *
+ * Copyright (C) 2012 Rafael J. Wysocki <rjw@xxxxxxx>
+ */
+
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/pm_wakeup.h>
+
+#include "power.h"
+
+static struct workqueue_struct *autosleep_wq;
+static struct wakeup_source *autosleep_ws;
+
+static DEFINE_MUTEX(autosleep_lock);
+
+static suspend_state_t autosleep_state;
+
+static void try_to_suspend(struct work_struct *work)
+{
+ unsigned int initial_count, final_count;
+
+ if (!pm_get_wakeup_count(&initial_count, true))
+ goto out;
+
+ mutex_lock(&autosleep_lock);
+
+ if (!pm_save_wakeup_count(initial_count)) {
+ mutex_unlock(&autosleep_lock);
+ goto out;
+ }
+
+ if (autosleep_state == PM_SUSPEND_ON) {
+ mutex_unlock(&autosleep_lock);
+ return;
+ }
+ if (autosleep_state >= PM_SUSPEND_MAX)
+ hibernate();
+ else
+ pm_suspend(autosleep_state);
+
+ mutex_unlock(&autosleep_lock);
+
+ if (!pm_get_wakeup_count(&final_count, false))
+ goto out;
+
+ if (final_count == initial_count)
+ schedule_timeout(HZ / 2);
+
+ out:
+ queue_up_suspend_work();
+}
+
+static DECLARE_WORK(suspend_work, try_to_suspend);
+
+void queue_up_suspend_work(void)
+{
+ if (!work_pending(&suspend_work) && autosleep_state > PM_SUSPEND_ON)
+ queue_work(autosleep_wq, &suspend_work);
+}
+
+suspend_state_t pm_autosleep_state(void)
+{
+ return autosleep_state;
+}
+
+int pm_autosleep_set_state(suspend_state_t state)
+{
+#ifndef CONFIG_HIBERNATION
+ if (state >= PM_SUSPEND_MAX)
+ return -EINVAL;
+#endif
+ mutex_lock(&autosleep_lock);
+ __pm_stay_awake(autosleep_ws);
+ if (state == PM_SUSPEND_ON && autosleep_state != PM_SUSPEND_ON) {
+ autosleep_state = PM_SUSPEND_ON;
+ __pm_relax(autosleep_ws);
+ } else if (state > PM_SUSPEND_ON) {
+ autosleep_state = state;
+ __pm_relax(autosleep_ws);
+ queue_up_suspend_work();
+ }
+ mutex_unlock(&autosleep_lock);
+ return 0;
+}
+
+void pm_autosleep_lock(void)
+{
+ mutex_lock(&autosleep_lock);
+}
+
+void pm_autosleep_unlock(void)
+{
+ mutex_unlock(&autosleep_lock);
+}
+
+int __init pm_autosleep_init(void)
+{
+ autosleep_ws = wakeup_source_register("main");
+ if (!autosleep_ws)
+ return -ENOMEM;
+
+ autosleep_wq = alloc_ordered_workqueue("autosleep", 0);
+ if (autosleep_wq)
+ return 0;
+
+ wakeup_source_unregister(autosleep_ws);
+ return -ENOMEM;
+}
Index: linux/kernel/power/main.c
===================================================================
--- linux.orig/kernel/power/main.c
+++ linux/kernel/power/main.c
@@ -269,8 +269,7 @@ static ssize_t state_show(struct kobject
return (s - buf);
}

-static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
- const char *buf, size_t n)
+static suspend_state_t decode_state(const char *buf, size_t n)
{
#ifdef CONFIG_SUSPEND
suspend_state_t state = PM_SUSPEND_STANDBY;
@@ -278,29 +277,46 @@ static ssize_t state_store(struct kobjec
#endif
char *p;
int len;
- int error = -EINVAL;

p = memchr(buf, '\n', n);
len = p ? p - buf : n;

- /* First, check if we are requested to hibernate */
- if (len == 4 && !strncmp(buf, "disk", len)) {
- error = hibernate();
- goto Exit;
- }
+ /* Check hibernation first. */
+ if (len == 4 && !strncmp(buf, "disk", len))
+ return PM_SUSPEND_MAX;

#ifdef CONFIG_SUSPEND
for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {
if (*s && len == strlen(*s) && !strncmp(buf, *s, len))
break;
}
- if (state < PM_SUSPEND_MAX && *s) {
- error = enter_state(state);
- suspend_stats_update(error);
- }
+ if (state < PM_SUSPEND_MAX && *s)
+ return state;
#endif

- Exit:
+ return PM_SUSPEND_ON;
+}
+
+static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t n)
+{
+ suspend_state_t state;
+ int error = -EINVAL;
+
+ pm_autosleep_lock();
+ if (pm_autosleep_state() > PM_SUSPEND_ON) {
+ error = -EBUSY;
+ goto out;
+ }
+
+ state = decode_state(buf, n);
+ if (state < PM_SUSPEND_MAX)
+ error = pm_suspend(state);
+ else if (state > PM_SUSPEND_ON)
+ error = hibernate();
+
+ out:
+ pm_autosleep_unlock();
return error ? error : n;
}

@@ -341,7 +357,8 @@ static ssize_t wakeup_count_show(struct
{
unsigned int val;

- return pm_get_wakeup_count(&val) ? sprintf(buf, "%u\n", val) : -EINTR;
+ return pm_get_wakeup_count(&val, true) ?
+ sprintf(buf, "%u\n", val) : -EINTR;
}

static ssize_t wakeup_count_store(struct kobject *kobj,
@@ -349,15 +366,65 @@ static ssize_t wakeup_count_store(struct
const char *buf, size_t n)
{
unsigned int val;
+ int error = -EINVAL;
+
+ pm_autosleep_lock();
+ if (pm_autosleep_state() > PM_SUSPEND_ON) {
+ error = -EBUSY;
+ goto out;
+ }

if (sscanf(buf, "%u", &val) == 1) {
if (pm_save_wakeup_count(val))
return n;
}
- return -EINVAL;
+
+ out:
+ pm_autosleep_unlock();
+ return error;
}

power_attr(wakeup_count);
+
+#ifdef CONFIG_PM_AUTOSLEEP
+static ssize_t autosleep_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
+{
+ suspend_state_t state = pm_autosleep_state();
+
+ if (state == PM_SUSPEND_ON)
+ return sprintf(buf, "off\n");
+
+#ifdef CONFIG_SUSPEND
+ if (state < PM_SUSPEND_MAX)
+ return sprintf(buf, "%s\n", valid_state(state) ?
+ pm_states[state] : "error");
+#endif
+#ifdef CONFIG_HIBERNATION
+ return sprintf(buf, "disk\n");
+#else
+ return sprintf(buf, "error");
+#endif
+}
+
+static ssize_t autosleep_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t n)
+{
+ suspend_state_t state = decode_state(buf, n);
+ int error;
+
+ if (state == PM_SUSPEND_ON && strncmp(buf, "off", 3)
+ && strncmp(buf, "off\n", 4))
+ return -EINVAL;
+
+ error = pm_autosleep_set_state(state);
+ return error ? error : n;
+}
+
+power_attr(autosleep);
+#endif /* CONFIG_PM_AUTOSLEEP */
#endif /* CONFIG_PM_SLEEP */

#ifdef CONFIG_PM_TRACE
@@ -411,6 +478,9 @@ static struct attribute * g[] = {
#ifdef CONFIG_PM_SLEEP
&pm_async_attr.attr,
&wakeup_count_attr.attr,
+#ifdef CONFIG_PM_AUTOSLEEP
+ &autosleep_attr.attr,
+#endif
#ifdef CONFIG_PM_DEBUG
&pm_test_attr.attr,
#endif
@@ -446,7 +516,10 @@ static int __init pm_init(void)
power_kobj = kobject_create_and_add("power", NULL);
if (!power_kobj)
return -ENOMEM;
- return sysfs_create_group(power_kobj, &attr_group);
+ error = sysfs_create_group(power_kobj, &attr_group);
+ if (error)
+ return error;
+ return pm_autosleep_init();
}

core_initcall(pm_init);
Index: linux/drivers/base/power/wakeup.c
===================================================================
--- linux.orig/drivers/base/power/wakeup.c
+++ linux/drivers/base/power/wakeup.c
@@ -458,8 +458,10 @@ static void wakeup_source_deactivate(str
atomic_add(MAX_IN_PROGRESS, &combined_event_count);

split_counters(&cnt, &inpr);
- if (!inpr)
+ if (!inpr) {
wake_up_all(&wakeup_count_wait_queue);
+ queue_up_suspend_work();
+ }
}

/**
@@ -610,29 +612,33 @@ bool pm_wakeup_pending(void)
/**
* pm_get_wakeup_count - Read the number of registered wakeup events.
* @count: Address to store the value at.
+ * @block: Whether or not to block.
*
- * Store the number of registered wakeup events at the address in @count. Block
- * if the current number of wakeup events being processed is nonzero.
+ * Store the number of registered wakeup events at the address in @count. If
+ * @block is set, block until the current number of wakeup events being
+ * processed is zero.
*
- * Return 'false' if the wait for the number of wakeup events being processed to
- * drop down to zero has been interrupted by a signal (and the current number
- * of wakeup events being processed is still nonzero). Otherwise return 'true'.
+ * Return 'false' if the current number of wakeup events being processed is
+ * nonzero. Otherwise return 'true'.
*/
-bool pm_get_wakeup_count(unsigned int *count)
+bool pm_get_wakeup_count(unsigned int *count, bool block)
{
unsigned int cnt, inpr;
- DEFINE_WAIT(wait);

- for (;;) {
- prepare_to_wait(&wakeup_count_wait_queue, &wait,
- TASK_INTERRUPTIBLE);
- split_counters(&cnt, &inpr);
- if (inpr == 0 || signal_pending(current))
- break;
+ if (block) {
+ DEFINE_WAIT(wait);

- schedule();
+ for (;;) {
+ prepare_to_wait(&wakeup_count_wait_queue, &wait,
+ TASK_INTERRUPTIBLE);
+ split_counters(&cnt, &inpr);
+ if (inpr == 0 || signal_pending(current))
+ break;
+
+ schedule();
+ }
+ finish_wait(&wakeup_count_wait_queue, &wait);
}
- finish_wait(&wakeup_count_wait_queue, &wait);

split_counters(&cnt, &inpr);
*count = cnt;
--
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